1. Field of the Invention
The present invention is directed to systems, software, processes, and/or apparatus for detecting audio signal clipping. Accordingly, the general objects of the invention are to provide novel systems, software, methods, and/or apparatus such character.
2. Description of the Related Art
It is well known that audio signal sources have a finite output voltage level capability. Maximum output capability is typically determined by the supply voltage available to the audio components in the signal path. Audio signal clipping results when the output signal level exceeds the available supply voltage. Audio signal clipping is generally not desired because, when clipping occurs, the audio signal is no longer a linear representation of the original unclipped signal; this increases total harmonic distortion and reduces the quality of the audio signal. It is, therefore, generally preferred that the audio signals remain unclipped through the entire signal path to a listening device.
Such considerations are particularly important in automotive audio systems where a typical signal path may include one or more signal sources, preamplifiers, and power amplifiers that are separated from one another. If any one or more of the signal sources, preamplifiers, and power amplifiers exceed their capability, a clipped signal will result. Thus, various level-setting methods and apparatus have been employed to achieve maximum capability at each stage of the signal path and to minimize or eliminate clipping of the system as a whole.
If the maximum unclipped output voltage of an audio source is known, creating a fixed reference voltage for comparison to the known maximum output level would be a suitable method for clip detection and/or prevention. Current solutions of this nature involve monitoring the output of the amplifier to determine if a clipped signal is generated. Once a clipped signal is detected, the preamplified signal is adjusted to limit the amount of clipping. In, Botti et al. U.S. Pat. No. 5,068,620, the amplifier input voltage acts as a reference and is compared to the amplifier output. When the input voltage increases above the output voltage a detect signal is activated. In Buck et al. U.S. Pat. No. 5,430,409, the amplifier output voltage, minus fixed gain, is compared to the amplifier input voltage. A detect signal is activated when the input voltage exceeds the reference voltage. This method also incorporates an adjustable dc offset plus reference voltage which programs the total clipping distortion permitted before the detect signal is activated.
However, in many instances, the maximum unclipped output signal level from an audio source is unknown. In such instances, audio component input clip detection is desired.